The present invention relates to a device and process for joining and sealing sections of flexible material, such as material used to make up removable bladder tanks used to contain fuel or other liquids in aircraft or land vehicles, to aircraft or vehicle structure interior elements such as skins, ribs or bulkheads, for in-situ formation of a fluid tight container in the aircraft or vehicle.
Fuel containers for applications such as an aircraft typically face stringent weight and space requirements. Voids in structures such as fuselage and wing cavities are reserved to serve as fuel storage areas capable of storing substantial volumes of fuel. However, the voids are not simply filled with flammable fuel. Instead, various techniques have been developed for accommodating fuel storage requirements within such voids.
In one technique, the area within an aircraft fuselage or wing, is provided with an impervious bladder, formed outside of the aircraft and custom designed to accommodate the structural arrangement within the fuselage or wing. Various techniques have been proposed in relation to the construction of the bladder, the means for supporting the bladder within the structure, and the means for attaching the bladder to the structural members. While such bladder constructions are useful in that they provide a well-defined fuel containment area, they suffer from several generic technical and cost disadvantages. One such disadvantage relates to the need to custom design the bladder, outside of the aircraft or vehicle, to accommodate the specific structural arrangement and aircraft subsystems that must penetrate the structure and bladder. Abrasion of the bladder against protruding structural members may also be a concern, as well as the need to closely mate any support for the bladder about irregular structural features. Still further, mechanisms for securing the bladder to a structure may be cumbersome and expensive, particularly about irregular surface areas.
Another general technique for forming fuel compartments within an aircraft or vehicle is referred to as an integral construction technique. In that technique, no separate bladder is formed. Instead, interior cavities formed by structure surfaces of the fuselage or wing are sealed with hand applied or sprayed sealing materials which define a fluid chamber within the aircraft or vehicle (spaced from wing outersurface portions). The layers of sealing material may be formed in various ways, and in various configurations. Areas about irregular structural features may be sealed from the fluid chamber by selective placement of spacing material, with sealing material disposed upon the surface of the spacing material.
Such integral construction techniques have an advantage in that they do not require the external construction of a customized bladder, and avoid the difficulties that can be associated with subsystem penetrations and locating and securing such bladders. However, such integral construction techniques do not capitalize on the advantages of the bladder constructions, such as the additional containment integrity and fuel containment advantages associated with bladders. Moreover, such integral construction techniques may require tedious assembly insofar as the containment area is typically not complete until the fuselage and wing body is fully assembled, and containment integrity may be difficult to assure.
The present invention is directed to a structure and technique of forming hybrid fuel containers which capitalize on the advantages of both bladder construction and integral construction. By the present invention, a fuel container is constructed wherein certain portions are formed using an integral construction technique, particularly in areas where surface irregularities may make bladder construction cumbersome and less reliable. Other portions of the fuel container are defined by a section of flexible material, which is secured and sealed to the integrally-formed portion by a flexible transition joint to facilitate the definition of a continuous fuel container area. The flexible material may be conveniently joined to the integrally-formed portion prior to complete construction of the wing body such that the fuel container may be defined and inspected prior to complete assembly of the wing. The flexible material may be arranged in areas less subject to structural irregularity to multiple disadvantages associated with contemporary bladder constructions.